net/core/link_watch.c

   1 /*
   2  * Linux network device link state notification
   3  *
   4  * Author:
   5  *     Stefan Rompf <sux@loplof.de>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version
  10  * 2 of the License, or (at your option) any later version.
  11  *
  12  */
  13
  14 #include <linux/config.h>
  15 #include <linux/module.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/if.h>
  18 #include <net/sock.h>
  19 #include <net/pkt_sched.h>
  20 #include <linux/rtnetlink.h>
  21 #include <linux/jiffies.h>
  22 #include <linux/spinlock.h>
  23 #include <linux/list.h>
  24 #include <linux/slab.h>
  25 #include <linux/workqueue.h>
  26 #include <linux/bitops.h>
  27 #include <asm/types.h>
  28
  29
  30 enum lw_bits {
  31         LW_RUNNING = 0,
  32         LW_SE_USED
  33 };
  34
  35 static unsigned long linkwatch_flags;
  36 static unsigned long linkwatch_nextevent;
  37
  38 static void linkwatch_event(void *dummy);
  39 static DECLARE_WORK(linkwatch_work, linkwatch_event, NULL);
  40
  41 static LIST_HEAD(lweventlist);
  42 static DEFINE_SPINLOCK(lweventlist_lock);
  43
  44 struct lw_event {
  45         struct list_head list;
  46         struct net_device *dev;
  47 };
  48
  49 /* Avoid kmalloc() for most systems */
  50 static struct lw_event singleevent;
  51
  52 /* Must be called with the rtnl semaphore held */
  53 void linkwatch_run_queue(void)
  54 {
  55         LIST_HEAD(head);
  56         struct list_head *n, *next;
  57
  58         spin_lock_irq(&lweventlist_lock);
  59         list_splice_init(&lweventlist, &head);
  60         spin_unlock_irq(&lweventlist_lock);
  61
  62         list_for_each_safe(n, next, &head) {
  63                 struct lw_event *event = list_entry(n, struct lw_event, list);
  64                 struct net_device *dev = event->dev;
  65
  66                 if (event == &singleevent) {
  67                         clear_bit(LW_SE_USED, &linkwatch_flags);
  68                 } else {
  69                         kfree(event);
  70                 }
  71
  72                 /* We are about to handle this device,
  73                  * so new events can be accepted
  74                  */
  75                 clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
  76
  77                 if (dev->flags & IFF_UP) {
  78                         if (netif_carrier_ok(dev)) {
  79                                 WARN_ON(dev->qdisc_sleeping == &noop_qdisc);
  80                                 dev_activate(dev);
  81                         } else
  82                                 dev_deactivate(dev);
  83
  84                         netdev_state_change(dev);
  85                 }
  86
  87                 dev_put(dev);
  88         }
  89 }
  90
  91
  92 static void linkwatch_event(void *dummy)
  93 {
  94         /* Limit the number of linkwatch events to one
  95          * per second so that a runaway driver does not
  96          * cause a storm of messages on the netlink
  97          * socket
  98          */
  99         linkwatch_nextevent = jiffies + HZ;
 100         clear_bit(LW_RUNNING, &linkwatch_flags);
 101
 102         rtnl_shlock();
 103         linkwatch_run_queue();
 104         rtnl_shunlock();
 105 }
 106
 107
 108 void linkwatch_fire_event(struct net_device *dev)
 109 {
 110         if (!test_and_set_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state)) {
 111                 unsigned long flags;
 112                 struct lw_event *event;
 113
 114                 if (test_and_set_bit(LW_SE_USED, &linkwatch_flags)) {
 115                         event = kmalloc(sizeof(struct lw_event), GFP_ATOMIC);
 116
 117                         if (unlikely(event == NULL)) {
 118                                 clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 119                                 return;
 120                         }
 121                 } else {
 122                         event = &singleevent;
 123                 }
 124
 125                 dev_hold(dev);
 126                 event->dev = dev;
 127
 128                 spin_lock_irqsave(&lweventlist_lock, flags);
 129                 list_add_tail(&event->list, &lweventlist);
 130                 spin_unlock_irqrestore(&lweventlist_lock, flags);
 131
 132                 if (!test_and_set_bit(LW_RUNNING, &linkwatch_flags)) {
 133                         unsigned long thisevent = jiffies;
 134
 135                         if (thisevent >= linkwatch_nextevent) {
 136                                 schedule_work(&linkwatch_work);
 137                         } else {
 138                                 schedule_delayed_work(&linkwatch_work, linkwatch_nextevent - thisevent);
 139                         }
 140                 }
 141         }
 142 }
 143
 144 EXPORT_SYMBOL(linkwatch_fire_event);